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Title: Behaviour and strength of stiffened tubular T- and DT-joints in offshore structures
Author: Llewelyn-Parry, A.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2000
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This thesis addresses the understanding of the static strength and behaviour of internally ring stiffened T- and DT-joints under axial brace loading. Initial numerical work verifies the appropriateness of the Finite Element (F.E.) modelling technique and the use of the F.E. Method as an analysis tool. This was achieved through a validation study on both unstiffened and ring stiffened T-joints and on unstiffened DT-joints. There follows four substantial parametric studies on ring stiffened T- and DT-joints which investigate the effect of the variation of the stiffener dimensions of plain and T-shaped stiffeners along with the joint geometrical parameters β and γ on the strength and behaviour of the stiffener and the stiffened joint. Also the number and position of the ring stiffeners are investigated. Findings of the study enabled, where appropriate, the proposal of two methods of strength prediction for the ring stiffener. One uses Plastic Theory to postulate a ring model which is based on a five- or six-hinge failure mechanism for the stiffener, resulting in a virtual Work Equation. For this method it is assumed that a portion of the chord interacts with the stiffener in producing the strength enhancement. The stiffener cross-section is then considered as a T- and an I-section for the plain and T-shaped stiffeners respectively. The other is an empirical equation based on the variation of the non-dimensional stiffener strength with the various influencing non-dimensional parameters. It has been shown that the theoretical method can be compromised when the stiffener parameters exceed the validity range of the predictive method whereas the empirical method appears to be more robust to extrapolation of the validity ranges. Both methods provide accurate predictions of stiffener strength when compared to the newly created FE database and existing test and numerical results.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available